Saturation kinetics of iocetamic acid: Evaluation of indirect pharmacokinetic techniques and comparison with iopanoic acid

The biliary excretion of two oral cholecystographic contrast agents, iocetamic acid and iopanoic acid, were compared during low and high taurocholate infusion rates. The pharmacokinetics of these compounds after intravenous infusion were studied in bile-fistula dogs using both indirect and direct pharmacokinetic techniques. The indirect multiple infusion technique, corrected for urinary excretion, provides a reliable estimate of the maximum biliary excretion rates of either contrast agent without necessitating the sampling of biliary output. The results indicate that taurocholate facilitates the biliary excretion of both agents. At both taurocholate infusion rates studied, the maximum biliary excretion rate of iocetamic acid is greater than that of iopanoic acid.

The biliary and urinary excretion of sodium tyropanoate and sodium ipodate in dogs: pharmacokinetics, influence of bile salts and choleretic effects with comparison to iopanoic acid

The biliary and urinary excretion of sodium tyropanoate (Bilopaque) and sodium ipodate (Oragrafin) were studied in unanesthetized bile-fistula dogs using stepwise, increasing, intravenous infusions of the contrast materials. A constant intravenous infusion of sodium taurocholate was administered at the rate of either 0.5 or 2.0 mu moles per min per kg throughout each experiment. The biliary excretion of sodium tyropanoate or sodium ipodate was not effected by the rate of sodium taurocholate infusion. The maximum rate of biliary excretion of sodium ipodate was significantly greater than that of sodium tyropanoate with the low taurocholate infusion, but there was no significant difference between the two with the high taurocholate infusion. With the low taurocholate infusion the maximum biliary excretion rate of sodium tyropanoate (0.956 mu moles per min per kg) and sodium ipodate (1.472 mu moles per min per kg) were significantly greater than the maximum biliary excretion of iopanoic acid (Telepaque) (0.671 mu moles per min per kg). With the high taurocholate infusion the maximum biliary excretion rates of the three contrast agents were not statistically different. Both sodium tyropanoate and sodium ipodate produced an increase in canalicular bile flow (8-11 ml per millimole). These data suggest that in clinical cholecystography sodium tyropanoate and sodium ipodate are not excreted in bile more rapidly than iopanoic acid, except when the rate of biliary excretion of bile salts is low; that is, except in patients who are fasting or those who are on a fat-free diet.

Hepatic excretion of cholecystopaques introduced into the canine jejunum

The biliary excretion of five oral cholecystopaques was measured following their introduction into the jejunum of bile fistula dogs. The mean maximal iodine concentration in the bile ranged form a low of 2.2 +/- 0.55 mg per ml following a dose of 33 mg of iodine per kg of iopanoic acid to a high of 12.9 +/- 1.4 mg per ml after the same dose of sodium ipodate. Cumulative excretion at the end of three hours was over five times greater with sodium ipodate in comparison to ipoanoic acid. It is felt that the best explanation of this date is the ability of the more water soluble media to pass through the unstirred water layer of the intestine.

Radiopaque contrast media. XXXIX - Metabolism of iopronic acid by rat liver microsomes: characterization and identification of the metabolites

The metabolism of iopronic acid, 2(2[(3-acetamido-2,4,6-triiodophenoxy)ethoxy]methyl)butyric acid, was studied in vitro using rat liver microsomes as enzyme source. By means of solvent extraction, T.L.C., H.P.L.C. and mass spectrometry, the hydroxyethyl (3-acetamido-2,4,6-triiodophenyl) ether and the 3-acetamido-2,4,6-triiodophenoxyacetic acid have been identified as the metabolities of the parent drug. No deiodinated metabolites were found. The probable mechanism of the in vitro formation of the metabolites is discussed.

Pharmacology and physiology of the biliary radiographic contrast materials

(1) Solubilization of Telepaque in the intestine is a limiting factor in the rate of intestinal absorption. Bilopaque and Oragrafin are more water-soluble and appear to be better absorbed than Telepaque. (2) Bile salts in the intestinal lumen increase the solubility of Telepaque. Therefore, a fatty meal administered with the Telepaque is desirable to evacuate bile salts from the gallbladder into the intestine. This is not required for the more water-soluble agents, Biopaque and Oragrafin. (3) The degree of protein binding of the contrast agents can be related to the degree of toxicity. Cholografin is the most highly bound and is the most toxic. (4) Hepatic receptor proteins may specifically bind the biliary contrast agents. This may be the reason that the renal contrast materials are poorly escreted in bile compared to the biliary contrast agents. (5) Telepaque is conjugated in the liver with glucuronide making the compound more soluble in bile. This prevents precipitation of Telepaque in the gallbladder and avoids reabsorpiton from the intestine. (6) The biliary excretion of Telepaque is facilitated by bile salts. Therefore, the administration of a fatty meal with Telepaque not only increases the rate of intestinal absorption of Telepaque but also the rate of biliary excretion. (7) The rate of biliary excretion of both the oral and the intravenous contrast agents appears to be limited by a hepatic transport maximum. Above a certain dose, increased amounts of the contrast agents do not result in more rapid excretion of the agents into bile. Rapid infusion of intravenous contrast agents results in high plasma concentration and greater urinary excretion, without increasing the biliary excretion. It does not appear to be indicated in clinical practice. (8) The biliary concentration of the contrast agents used for intravenous cholangiography is determined by their rate of biliary excretion, the choleretic effect of the contrast agent, and factors that determine the rate of basal bile flow. Fixed coupling of water with the biliary excretion of these contrast agents imposes an inherent limitation on the concentration of the contrast agent in bile. It appears that the biliary concentration of the intravenous contrast materials can be increased by having the patient fast prior to intravenous cholangiography. This decreases the enterohepatic circulation of bile salts and the rate of bile-salt-dependent bile flow. (9) Failure of the gallbladder to visualize after administration of Telepaque when there is adequate biliary excretion may be due to cystic duct obstruction, failure of the inflamed gallbladder mucosa to reabosrb water, or reabsorption or the contrast agent by the diseased gallbladder mucosa. (10) Maximum concentration of Telepaque occurs at 14-19 hr after ingestion. It is at this time that radiographs of the gallbladder should be made. With Bilopaque, peak concentration occurs at 10 hr so radiographs can be made earlier when Bilopaque is used.

Influences on the rate of absorption of the cholecystographic contrast medium iosumetic acid in man

Groups of 5 fasting male and female patients aged 32-83 years were each given 3 gm of the cholecystographic contrast medium iosumetic acid in micronized form (particle size less than 20 mum); Group I with 150 ml tea (standard administration); Group II with 500 ml tea; Group III with 150 ml tea plus 10 mg metoclopramide (Paspertin) 5 min p. admin. i.v.; and Group IV with 150 ml tea and 3 gm sodium bicarbonate. Blood samples were taken in the period up to 6 hours after administration in order to determine the iodine concentration according to the method of Juegst and Stauch. In Groups I and II maximum blood levels were reached 2.1 +/- 0.4 or 2.0 +/- 0.4 h p. admin. respectively, in Group III 1.6 +/- 0.2 h p. admin (in comparison to Group I: p less than 0.05) and in Group IV the maximum level was reached after only 0.9 +/- 0.2 h p. admin. The difference between Group IV and the other three groups is statistically significant (p less than 0.01). A half-life of 0.3 +/- 0.1 h was calculated for absorption in Group IV.

Radiopague contrast media. Part 30. New heterocyclic derivatives of triiodophenoxy alkanoic acids

A series of new heterocyclic derivatives of triiodophenyl and triiodophenoxy alkanoic acids was prepared; some of these compounds showed high billiary excretion and low acute toxicity in rats. One compound, 2-ethyl-3-[3-N-butyrolactamyl-2,4,6-triiodophenyl]-propionic acid, showed such characteristics that encouraged us to carry out further preclinical and clinical investigations.

Two hepatic cytoplasmic protein fractions, Y and Z, and their possible role in the hepatic uptake of bilirubin, sulfobromophthalein, and other anions

Two hepatic cytoplasmic protein fractions, designated Y and Z, which bind sulfobromophthalein (BSP), bilirubin, and other organic anions, have been separated by G75 Sephadex gel filtration. The physiologic role of these protein fractions has been investigated. They are present in the 110,000 g supernatant fraction from the livers of all the species tested (rats, mice, guinea pigs, Rhesus monkeys, sheep, and man). Tissues which do not preferentially extract BSP or bilirubin from plasma do not contain these fractions, with the exception of small intestinal mucosa which contains Z. Anion binding by Y and Z fractions is not due to contamination with albumin. These fractions are responsible for the cytoplasmic localization of bilirubin in Gunn rats, and the fractions bind bilirubin, BSP, or indocyanine green (ICG), whether given in vivo or added in vitro to liver supernate from normal rats. Flavaspidic acid-N-methylglucaminate, bunamiodyl, and iodipamide, drugs known to interfere with the hepatic uptake mechanism, compete with bilirubin and BSP for binding to Z. These proteins appear to be important in the transfer of organic anions from plasma into the liver and provide a tool for the investigation of hepatic uptake mechanisms.